Although it's billed as a brusher blush, the Sonia Kashuk Synthetic Flat Top Brush h has been getting raves for liquid foundation application. Two Sigma brushes I have, the Flat Top Kabuki F80, as well as the Round Top Kabuki F82, are quite similar to the brushes. Since I've already talked about the Flat Top Kabuki before, I thought I'd deal with the Round Top Kabuki in this one.
Both brushes are similar, and both are of surprisingly good quality, considering the price. Both have synthetic bristles, and the bristles are quite densely packed. Both also have a similar brush diameter. In many respects, the similarities in bristle type and density mean that both brushes will be pretty similar. If you liked the Sonia Kashuk for liquid application, you'd probably like the Sigma Kabuki for a similar effect, too. If you liked the Sonia Kashuk for buffing and blending, you'd probably like the Sigma Round Top for the same, too. And if you liked the small, handy size of the Sonia Kashuk brush for working around tiny areas of the face, like the nose, then the Sigma Kabuki would perform in exactly the same way.
That said, there are some slight differences. The Sonia Kashuk Flat Top Brush has bristles that are slightly longer than the sigma Kabuki, and the Sigma Round Top Kabuki has a brush shape that is slightly rounded at the sides, whereas the Sonia Kashuk is totally flat. Thus, the Sigma brush is more likely to give a denser application of product as compared to the Sonia Kashuk brush. Also, some people might prefer the rounded shape of the Sigma Kabuki, as they feel it might help them maneuver around the contours of their faces better. The differences may not be very noticeable, but I'm splitting hairs for the sake of a review here.
So which one do you need? Well, I'd say both are pretty compable, and I guess ultimately which one you end up with would depend on which one is available. For girls who live outside of the USA (or for that matter, within the USA but far away from a Target), where Sonia Kashuk is unavailable or hard to get, then the Sigma Round Top Kabuki or Flat Top Kabuki would be a very close substitute. Sigma Beauty does ship worldwide, so it's easily gotten hold of.
(The Sigma brush was sent to me for review. Review is my complete and honest opinion. I am not compensated or affiliated with the company in any way.)